The announcement comes after a spate of alleged sorcery killings in the Pacific nation this year.

The most recent was on the island of Bougainville, where an angry mob last week beheaded an elderly woman accused of practicing sorcery or black magic.

Researchers say the Sorcery Act legitimises such murders by making sorcery a legally recognised phenomenon and its practice a criminal offence.

Mr O'Neill says his government will repeal the law.

"To stop this nonsense about witchcraft and all the other sorceries that are really barbaric," he said.

Mr O'Neill says the act could be scrapped in the next sitting of parliament, or later in the year.

North Bougainville Human Rights Committee's chairperson, Helen Hakena, says Mr O'Neill's announcement shows there is genuine political will to stamp out sorcery killings.

"For us women we are so happy that our country's leaders - particularly the prime minister - is looking into that because that will really help to promote and protect the human rights of our people accused of sorcery," she said.

"And that will help bring justice to those perpetrators who are accusing people of sorcery and killing them."

Police powerless

Police say they do not have the resources or manpower to respond to sorcery-related violence in Bougainville

Last Tuesday Helen Rumbali and her sister Nikono and Nikono's two teenage daughters were kidnapped by a mob and taken to Lopele village in the Bana district.

The women were accused of using sorcery, or black magic, to kill someone.

After torturing the women for several days, the mob murdered Ms Rumbali by cutting her head off.

The acting assistant police commissioner for south Bougainville, Paul Kamuai, says local forces were unable to stop the violence.

"This was an extraordinary situation that men and women were there, and it was at night," he said.

"And then we found out that there were arms around, and we couldn't use the arms - there would have been a lot of killing from the police and then from the civilians as well."

After negotiations with community leaders, the mob allowed Nikono and her daughters to go to a local health clinic but they have set up a roadblock preventing them from leaving the area.

Nikono Rumbali is believed to be in a critical condition after the mob tried unsuccessfully to decapitate her.

But Mr Kamuai says there are no plans to arrest the murderers or rescue the three women still being held captive.

He says police are outnumbered and outgunned.

"Police on Bougainville are not armed. Even if we're armed, there are more arms still out there," Mr Kumuai said.

"I have eight regular police. They do not have a proper police station - they live in the villages.

'Very sad situation'

Bougainville is awash with guns, a result of the bitter civil war fought there during the 1990s.

The fighting ended with a peace agreement in 2001, but disarmament efforts have since stalled. There are plenty of factory and home-made weapons in the hands of ex-combatants and others.

Human rights group Amnesty International says the lack of action from police is not good enough.

"If all the police can do is stand by and watch while women are executed, that's a very sad situation for the country indeed," Amnesty's Pacific researcher Kate Schuetze said.

Ms Schuetze says the PNG Government must provide police with the resources they need to do their jobs.

"I understand that there are limitations with resources but it's not an adequate excuse the government to say they can't protect someone's life and meet their responsibilities... just because they don't have the capacity."

Widespread beliefs

Sorcery killings are not uncommon in Papua New Guinea.

In February a woman who was burnt alive on a street in Mt Hagen, the biggest town in PNG's highlands, made headlines around the world.

But residents in Bougainville say the murder of Helen Rumbali is the first sorcery killing on their island.

NBHRC's Helen Hakena believes the murderers have used sorcery as a cover for other motives.

"It's pure jealousy of a family who is well known, that they've got positions in government. And this woman is a woman leader and they've got good homes," she said.

Ms Hakena says women are horrified at what has happened and they too want the police to take action.

"If this one woman is not respected then all of us will face the same consequences," she said.

A request for comment has been declined by Bougainville affairs minister, Steven Kamma.